Which of the following is not a Bronsted acid

Options

A. `CH_(3)NH_(4)^(+)`
B. `CH_(3)COO^(-)`
C. `H_(2)O`
D. None

Answer

To determine which of the following substances is not a Bronsted acid, we first need to understand the definition of a Bronsted acid. A Bronsted acid is a substance that can donate a proton (H⁺ ion) to another substance.

Let's analyze each option provided:

1. **CH₃NH₄⁺ (Methylammonium ion)**: This ion can donate a proton to form CH₃NH₂ (methylamine). Therefore, it acts as a Bronsted acid.

2. **CH₃COOH (Acetic acid)**: Acetic acid can donate a proton to form CH₃COO⁻ (acetate ion). Hence, it is also a Bronsted acid.

3. **H₂O (Water)**: Water can donate a proton to form OH⁻ (hydroxide ion). Thus, water is also a Bronsted acid.

4. **CH₃COO⁻ (Acetate ion)**: This ion cannot donate a proton; instead, it can accept a proton to form CH₃COOH. Therefore, it does not act as a Bronsted acid.

Based on this analysis, the substance that is not a Bronsted acid is **CH₃COO⁻ (acetate ion)**.

### Final Answer:
**CH₃COO⁻ (Acetate ion)** is not a Bronsted acid.

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